The activation of metallorganic chemical vapor deposition-grown Mg-doped GaN by N-2 annealing with thin Co and Pt films has been investigated. The Hall effect measurements revealed that both the Co and Pt films enhance activation of Mg acceptors as catalysts at low temperatures. A maximum hole concentration of p-type GaN was achieved at annealing temperature of 600 degreesC for the samples activated with both the Co and Pt films. It was also revealed that the activation of the acceptors is strongly affected by the thickness of the Co film. (C) 2002 Elsevier Science B.V. All rights reserved.